1. Field of the Invention
This invention relates generally to a system and method for determining vehicle wheel imbalance and, more particularly, to a system and method for determining that a particular wheel of a vehicle is out of balance using wheel angle signals from the wheels and a vibration measurement at a response point on the vehicle that includes calculating a recursive least squares solution from the wheel angle signals and the vibration measurements.
2. Discussion of the Related Art
Wheel imbalance is a common problem that owners of a vehicle often experience. Wheel imbalance usually manifests itself through vibrations at the steering wheel, which become more pronounced at higher vehicle speeds. There are many causes for wheel imbalance and associated vibrations at the steering wheel. For example, the wheels and/or tires may have developed defects over time. Also, imbalances could occur from denting the wheel by hitting a curb, which may change the wheel's physical dimensions, and therefore, destroy the symmetry of the wheel that would result in vibrations. Further, wheel imbalance induced vibrations is one of the major causes of failure or degradation of vehicle chassis systems, such as steering and suspension. Thus, left untreated, wheel imbalance may lead to excessive degradation of chassis components, such as bearings, bushings, etc.
When a customer services a vehicle wheel imbalance problem, typically only the presence of the vibration is communicated to the service personnel. A technician then has to remove each wheel of the vehicle, mount it on a wheel balance machine, and make necessary adjustment to quell rotational imbalance. This process of “hunting” for the suspect wheel location that causes the imbalance presents an opportunity. If the location of wheel imbalance (e.g., left front vs. right rear wheels) could be identified in advance, it would save time currently used in locating the suspect wheel, which would reduce the warranty cost dramatically. Moreover, detecting imbalances during vehicle operation, and re-balancing the wheel at an early stage can prevent the propagation of harmful vibration to other chassis components. This will reduce chassis component failure and associated warranty costs.